Webster's New World Medical Dictionary

sinus tachycardia
Fast heartbeat (tachycardia)
that occurs because of overly rapid firing by the
sinoatrial node. Sinus tachycardia is usually a rapid
contraction of a normal heart in response to a con-
dition, drug, or disease, such as pain, fever, exces-
sive thyroid hormone, exertion, excitement, low
blood oxygen level (hypoxia), or stimulant drugs,
such as caffeine, cocaine, and amphetamines.
However, in some cases sinus tachycardia can be a
sign of heart failure, heart valve disease, or other 
illness.
sinusitis
Inflammation of the lining membrane in
any of the hollow areas (sinuses) of the skull around
the nose. Sinusitis may be caused by anything that
interferes with air flow into the sinuses and the
drainage of mucous out of the sinuses. The sinus
openings, called ostia, may be obstructed by swelling
of the tissue lining the ostia and adjacent nasal pas-
sage tissue; for example, from colds, allergies, and
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tissue irritants (nasal sprays, cocaine, cigarette
smoke). Less commonly, sinuses can become
obstructed by tumors or growths. Stagnated mucous
then provides a perfect environment for bacterial
infection. The common symptoms of sinusitis
include headache; facial tenderness or pain; fever;
cloudy, discolored nasal drainage; a feeling of nasal
stuffiness; sore throat; and cough. Acute sinusitis is
usually treated with antibiotic therapy. Chronic forms
of sinusitis require long courses of antibiotics and
may require a sinus drainage procedure.
situational syncope
See 
syncope, situational.
situs inversus totalis
See 
reversal of organs,
total.